1. Field of the Invention
The present invention generally relates to a semiconductor device, a method of manufacturing a semiconductor device and a method of manufacturing a lead frame, and particularly relates to a semiconductor device having high-density external-connection electrodes, a method of manufacturing such a semiconductor device and a method of manufacturing a lead frame.
Recently, there is a need for semiconductor devices having smaller mounting areas on supporting boards so as to realize miniaturization of electronic devices. Also, there is a need for fine-pitched semiconductor devices in respect to the pitches of electrodes and of external connection terminals.
2. Description of the Related Art
FIGS. 1A to 1C and FIG. 2 are diagrams showing resin-seal type semiconductor devices of the related art.
Referring to FIGS. 1A to 1C, a first resin-seal type semiconductor device includes a resin 1, a semiconductor chip 2, outer leads 3, bonding wires 4 and a die pad 5. This semiconductor device has a package structure called SSOP (Shrink Small Outline Package) and is mounted on a supporting board with the outer leads 3 bent in a gull-wing shape.
Referring to FIG. 2, a second resin-seal type semiconductor device is provided with the resin 1, the semiconductor chip 2, the bonding wires 4, solder balls 6 and a semiconductor chip mounting board 7 whereon the semiconductor chip 2 is mounted. This semiconductor device has a package structure called BGA (Ball Grid Array), and terminal parts mounted on the mounting board are formed of solder balls 6.
With the semiconductor device of the SSOP type as shown in FIGS. 1A to 1C, there is a problem that the mounting area becomes large. This is because a connection part 9 between inner leads 8 in the resin 1 and the outer leads 3, and the outer leads 3 both occupy comparatively large areas. Also, with the semiconductor device of the BGA type shown in FIG. 2, there is a problem of additional cost since the device requires the mounting board 7.
In order to provide a semiconductor device which can solve the above-described problems, the applicant has proposed Japanese Laid-Open Patent Application 9-162348. FIG. 3 shows a semiconductor device 110 related to the cited application.
The semiconductor device 110 shown in FIG. 3 has a package structure called BCC (Bump Chip Carrier) and has an extremely simple structure including a semiconductor chip 111, a resin package 112 and metal layers 113. The metal layers 113 are deposited on resin protrusions 117 integrally formed on a mounting surface 116 of the resin package 12. The semiconductor chip 111 is connected to the metal layers 113 by wires 118. Also, stud bumps 119 are provided so as to improve connectivity between the wires 118 and the metal layers 113.
The semiconductor device 110 having the above structure no longer requires inner leads and outer leads as those of the SSOP type of the related art. Therefore, no area is required for the connection part between the inner leads and the outer leads and for the outer leads. Thus, the semiconductor device 110 can be miniaturized.
Also, a mounting board as used in the BGA type of the related art is no longer required since there is no need for supporting the solder balls thereon. Therefore, the cost of manufacturing the semiconductor device 110 can be lowered. Further, the resin protrusions 117 and the metal layers 113 cooperate so as to provide a function equivalent to that of the solder bumps of the semiconductor device of the BGA type. Thus, a mounting ability can be improved.
However, problems may arise when attempting to provide fine-pitched external connection terminals having a terminal pitch size of, for example, less than 0.5 mm so as to meet the recent trend of ever miniaturized and fine-pitched semiconductor devices. With the semiconductor device 110 of the BCC structure shown in FIG. 3, the external connection terminals are formed of the resin protrusions 117 and the metal layers 113. Thus, it is difficult to achieve a fine-pitched structure in regards to creating half-etched recesses of the lead frame during manufacturing processes of the semiconductor device and to creating the metal layers 113. In other words, there is a limit in reducing the mounting area. Therefore, there is still a need for further reduction in the mounting area.
Also, with the semiconductor device of the BGA structure shown in FIG. 2, a fine-pitched structure of the semiconductor device implies finer solder balls 6. It is then difficult to mount such fine solder balls 6 on the semiconductor mounting board 7 with high accuracy.
Accordingly, there is a need for a resin-seal type semiconductor device having fine-pitched mounting terminals and a small mounting area, while achieving reduction in its cost and size. Also, there is a need for a method of manufacturing such a semiconductor device. Further, there is a need for manufacturing a lead frame.
Accordingly, it is a general object of the present invention to provide a semiconductor device, a method of manufacturing a semiconductor device and a method of manufacturing a lead frame which can satisfy the needs described above.
It is another and more specific object of the present invention to provide a semiconductor device which can achieve a fine-pitched structure of external connection terminals.
In order to achieve the above objects according to the present invention, a semiconductor device includes a semiconductor chip sealed in a resin and connecting members for electrically connecting the semiconductor chip and external connection terminals, wherein the external connection terminals are stud bumps.
In the semiconductor device described above, when wires are used as the connecting members, stud bumps can be formed with the same equipment as used in a wire bonding process, since a wire bonder is used for forming the stud bumps. Therefore, an equipment cost can be reduced.
It is still another object of the present invention to provide a semiconductor device which can achieve a fine-pitched structure of external connection terminals and also a low-back structure of the semiconductor device.
In order to achieve the above object, a semiconductor device includes a semiconductor chip, a resin package for sealing the semiconductor chip, metal layers provided on a mounting-side surface of the resin package in an exposed manner and connecting members for electrically connecting electrode pads provided on the semiconductor chip and the metal layers. The metal layers are provided with stud bumps on the mounting side, the stud bumps serving as external connection terminals.
It is yet another object of the present invention to provide a semiconductor device which can achieve good electrical connectivity between the semiconductor chip and metal layers, and between the metal layers and the mounting board.
In order to achieve the above object, each of the metal layers has a single-layered structure and is made of one of gold (Au), palladium (Pd) and aluminum (Al). Other embodiments are also possible. Each of the metal layers may have a double-layered structure having two layers each made of respective one of gold (Au), palladium (Pd) and aluminum (Al). Each of the metal layers may have a double-layered structure having an outer layer made of palladium (Pd) and an inner layer made of nickel (Ni). Also, each of the metal layers may have a triple-layered structure having three layers made of either a combination of an outer layer made of palladium (Pd), an intermediate layer made of nickel (Ni) and an inner layer made of palladium (Pd), or a combination of an outer layer made of gold (Au), an intermediate layer made of nickel (Ni) and an inner layer made of palladium (Pd). Further, each of the metal layers may have a quadruple-layered structure having four layers made of a combination of an outer layer made of palladium (Pd), a first intermediate layer made of nickel (Ni), a second intermediate layer made of palladium (Pd) and an inner layer made of gold (Au).
It is yet another object of the present invention to provide a semiconductor device which can achieve a further high-density structure of the external connection terminals.
In order to achieve the above object, a semiconductor device includes a semiconductor chip, a resin package for sealing the semiconductor chip and connecting members having one set of ends connected to electrode pads on the semiconductor chip and the other set of ends exposed from the resin package as to form mounting-side ends, wherein the mounting-side ends exposed from the resin package are provided with stud bumps, the stud bumps serving as external connection terminals.
It is yet another object of the present invention to provide a semiconductor device which can provide the wires efficiently and at a low cost.
In order to achieve the above object, connecting members are wires. Therefore, a wire bonding equipment can be used which is commonly used as equipment for manufacturing semiconductor devices.
It is yet another object of the present invention to provide a semiconductor device which can achieve a low-back structure of wire loops so as to reduce the thickness of the semiconductor device.
In order to achieve the above object, the wires extend from the stud bumps and terminate at electrode pads on the semiconductor chip. A joining area against the stud bump will be greater since an end of the wire which is joined to the stud bump becomes the first bonding side. Therefore, a joining ability between the stud bumps and the wires is improved.
It is yet another object of the present invention to provide a semiconductor device which can prevent bad connections of the stud bumps and improve the reliability of the semiconductor device.
In order to achieve the above object, an area of a part of the connecting members exposed from the resin package is greater than a joining area of the stud bump. When automatically forming the stud bumps using the wire-bonding equipment, the stud bumps can be securely joined on the first bonding parts since slight errors of bonding positions do not affect the joining of the stud bumps and the first bonding parts.
It is yet another object of the present invention to provide a lead frame used for manufacturing the semiconductor described above, which has a simple structure.
In order to achieve the above object, the metal layers are provided at positions corresponding to positions where the stud bumps are to be provided.
It is yet another object of the present invention to provide a lead frame used for manufacturing the semiconductor described above, which can prevent the resin package from falling off from the lead frame, thus improving a yield of manufacturing the semiconductor device.
In order to achieve the above object, a recessed part is formed at a position corresponding to a position where the resin package is to be formed. Also, the lead frame can further include an intermediate metal layer provided inside the recessed part. Further, the recessed part has an area, at least at the periphery, not provided with the intermediate metal layer. Finally, the recessed part can be provided with raised parts formed therein.
It is yet another object of the present invention to provide a simple method of manufacturing the lead frame.
In order to achieve the above object, the method of manufacturing the lead frame includes the steps of:
a) forming a first resist on a base material;
b) forming a predetermined first resist pattern by removing parts of the first resist corresponding to the parts where through holes are to be formed, the through holes used for fixing or moving the base material;
c) forming through holes by etching the base material using the first resist pattern as a mask;
d) removing the first resist;
e) forming a second resist on a base material;
f) forming a predetermined second resist pattern by forming resist openings by removing parts of the second resist corresponding to the parts where metal layers are to be formed;
g) forming metal layers at the resist openings formed on the second resist; and
h) removing the second resist.
It is yet another object of the present invention to provide a method of manufacturing the semiconductor device with simple manufacturing processes.
In order to achieve the above object, the method includes the steps of:
a) mounting the semiconductor chip on the lead frame, and electrically connecting the semiconductor chip and the metal layers using the connecting members;
b) sealing the semiconductor chip on the lead frame so as to form the resin package;
c) dissolving the lead frame so that the metal layers are exposed;
d) forming stud bumps on a mounting-side surface of the exposed metal layers.
Alternatively, the method can include the steps of:
a) mounting the semiconductor chip on the lead frame, and electrically connecting the semiconductor chip and the metal layers using the connecting members;
b) sealing the semiconductor chip on the lead frame so as to form the resin package;
c) dissolving the lead frame and the metal layers so that mounting-side ends of the connecting members are exposed;
d) forming stud bumps on the exposed mounting-side ends of the connecting members.
It is yet another object of the present invention to provide a method of manufacturing the semiconductor device which method can form external plating on a number of mounting- side ends provided with a fine structure.
In order to achieve the above object, the method includes the steps of:
a) mounting the semiconductor chip on the lead frame, and electrically connecting the semiconductor chip and the metal layers using the connecting members;
b) sealing the semiconductor chip on the lead frame so as to form the resin package;
c) dissolving the lead frame and the metal layers so that mounting-side ends of the connecting members are exposed;
d) forming external plating on the exposed mounting-side ends of the connecting members.
It is yet another object of the present invention to provide a method of manufacturing the semiconductor described above, which can prevent the resin package from falling off from the lead frame, thus improving a yield of manufacturing the semiconductor device.
In order to achieve the above object, the method includes the steps of:
a) mounting the semiconductor chip in the recessed part formed in the lead frame, and forming connecting members having one set of ends connected to electrode pads on the semiconductor chip and the other set of ends exposed from the resin package so as to form mounting-side ends;
b) sealing the semiconductor chip in the recessed part formed in the lead frame so as to form the resin package;
c) dissolving the lead frame so that the mounting-side ends of the connecting members are exposed;
d) forming stud bumps on the exposed mounting-side ends of the connecting members.
Also, the connecting members may be one of wires and protruded electrodes. When the connecting members are wires, the step a) further includes the steps of:
e) first bonding the wires on the intermediate metal layer, and
f) second bonding the wires on the semiconductor chip by extending the wires.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.